Systems are known for signal amplification, whereof the frequency bandspread is large. However, these systems have the drawback of causing excessive energy consumption, when they are used for amplifying signals having a narrow frequency bandspread typically less than one octave. In the case of signals having a narrow frequency bandspread, the efficiency of these systems is then very bad, it is then necessary to increase the power of the transmission circuits. This increase leads to a need for cooling these systems, a cooling device which is also energy-consuming.
Document EP2159912 describes a Doherty amplification system including a main amplifier with a relatively wide band and two auxiliary amplifiers with a narrower band. The auxiliary amplifiers operate in a mutually exclusive way; their bands are included in that of the main amplifier. This amplification system presents a relatively narrow band, much less than one octave, notably because of the use of quarter-wave phase shifters.
Systems are known which comprise a set of sensors having different functions or a set of antennas, and which distribute the received signals in different subbands. These systems then amplify the signals by subbands. However these systems are not adaptive in frequency and/or in power and efficiency, and therefore may not be adapted to the amplification of signals whereof the frequency bandspread is not known a priori.
Class switching is a known operation for increasing the efficiency of amplifiers.